1. Field of the Invention
The present invention pertains to a film transport device for cinematographic cameras and projectors with an intermittently operating film feed device and with a rotary shutter, wherein the film feed device engages perforations of the film and is driven by a drive motor which can be controlled synchronously with the separately driven rotary shutter.
2. Description of the Prior Art
A single, common motor has been used in most of the movie cameras and movie projectors used hitherto for driving all movable parts of the film transport device and of the shutter, because of the necessity to synchronously control these parts. As a consequence of this, complicated gear mechanisms are necessary, which have to transform the continuous movement of the drive into the intermittent movement of the film.
Mechanical pin assemblies are used for the film transport, especially in movie cameras. A pin which is steadily in motion periodically engages in the perforations of the film in order to forward it. In order for the pin tip to describe a suitable path, a very complicated mechanical structure is necessary. Despite a relatively slow film transport, the film is strongly compromised by the pin assembly. In addition, the mechanism generates considerable running noise, which is particularly disadvantageous in the case of simultaneous shooting and sound recording.
The tripping mechanisms, which are used primarily in projectors, in which several teeth of a toothed film feed drum are steadily engaged in the perforations of the film, and which periodically rotate further by a well-defined angle in order to transport the film, compromise the film much less. The common tripping mechanisms with Geneva motion drive are, however, also very noisy and are particularly not suitable for use in movie cameras because of their complicated structure.
A film transport device for movie projectors is known from DE-OS No. 28 18 910, which discloses a tripping mechanism with separate drive motors for the rotary shutter and for the film feed. The drive motor for the film feed is a stepping motor whose drive pulses are synchronized with the rotation of the rotary shutter. This film transport device has the disadvantage that the stepping motor must operate very exactly to achieve a sufficiently good picture steadiness, i.e., both the control and the motor itself must be of an expensive design. In particular, this requires the stepping motor to be designed to be relatively large and heavy, whereby the possible applications in portable units are greatly restricted. In addition, it is difficult to optimize the stepping motor in terms of high accuracy, high speed and gentle film transport.